In the construction of turbines (e.g., steam turbines), cover plates are employed for a variety of reasons and are generally secured to the tips of turbine buckets by peening fasteners formed on the buckets. To secure the bucket tips and cover plates to one another, solid fasteners on the bucket tips are peened into the bucket cover openings.
It is sometimes necessary to remove the cover plates in order to repair the buckets or to replace the cover plates. Currently, removal of the turbine bucket cover plates is a manual process that requires a repair technician to hold a pneumatic grinder with an abrasive disc and guide the grinder over the top of the cover. This process exposes the technician to dust from the abrasive wheel, noise at a close distance from the grinder, flying sparks and debris from the wheel, and fatigue from holding the tool. The depth of cut using the manual process may vary depending on the skill of the technician. If the cut is too deep the tip of the bucket vane can be damaged which could lead to an extensive repair or bucket replacement.
A method for removing bucket covers that does not require the use of manual cutting tools is accomplished by placing the turbine rotor into a rotor turning device or lathe. A tool bit is used to cut the covers up to the tenons of the buckets as the rotor is rotating at a constant speed. One drawback of this method is that a rotor turning device, tool compound, and cutting tools are needed to remove the covers. With the robotic cutting system a turning device or lathe is not required.
What is needed is a system that allows for the operator to remain at a distance from the cutting operation and reduces the possibility of inhalation of grinding dust, debris in the eyes, and operator fatigue, and to precisely control the cuts made on each bucket cover. Also needed is a programmable robotic method and apparatus for cutting bucket covers which may virtually eliminate the possibility of cutting into a vane tip, and so that a steel grinding wheel may be used repeatedly without changing.